U.S. patent number 5,332,049 [Application Number 07/953,013] was granted by the patent office on 1994-07-26 for composite drill pipe.
This patent grant is currently assigned to Brunswick Corporation. Invention is credited to Craig Tew.
United States Patent |
5,332,049 |
Tew |
July 26, 1994 |
Composite drill pipe
Abstract
A composite drill pipe has a fiber reinforced synthetic tube
with a leading end and a trailing end spaced axially from the
leading end, with the leading end of the tube being engageable with
a bit for drilling a bore through the earth when a force is applied
to the trailing end of the tube. Hardened steel fittings are
attached to the opposite tube ends and have interengageable
threaded portions for joining a plurality of serially arranged
drill pipes and forming a flexible drilling string of desired
length. Radial holes are drilled around the circumference of the
tube ends and into the steel fittings, and stainless steel dowel
pins are press fit into the holes to provide a mechanical lock
between the composite tube and the fittings. A steel sleeve is
placed over the is bonded to the outer surface of the tube. A
series of steel-encased centralizer buildups are spaced along the
length of the composite tube to align the tube within the well bore
and to prevent contact between the tube exterior and the sidewalls
of the bore when the tube is advanced therethrough.
Inventors: |
Tew; Craig (Lincoln, NE) |
Assignee: |
Brunswick Corporation (Lake
Forest, IL)
|
Family
ID: |
25493460 |
Appl.
No.: |
07/953,013 |
Filed: |
September 29, 1992 |
Current U.S.
Class: |
175/320; 138/109;
166/242.6; 175/325.2; 285/222.1 |
Current CPC
Class: |
E21B
17/00 (20130101); E21B 17/04 (20130101); E21B
17/1078 (20130101); E21B 17/20 (20130101); F16L
47/24 (20130101) |
Current International
Class: |
E21B
17/10 (20060101); E21B 17/02 (20060101); E21B
17/20 (20060101); E21B 17/04 (20060101); E21B
17/00 (20060101); F16L 47/00 (20060101); F16L
47/24 (20060101); E21B 017/04 (); E21B 017/10 ();
E21B 017/20 () |
Field of
Search: |
;175/320,325.1,325.2
;166/242,241.1 ;138/109,143,155 ;285/149,238,239,242 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Buckle Resistant Composite Drill String For Extended Reach and
Horizontal Drilling (AEA Petroleum Services) &
(Rogalandsforskning) (61 pages)..
|
Primary Examiner: Dang; Hoang C.
Attorney, Agent or Firm: Wood, Phillips, VanSanten, Hoffman
& Ertel
Claims
I claim:
1. A pipe for drilling a well bore, comprising:
a fiber reinforced synthetic tube, the tube having a leading end
and a trailing end spaced axially from the leading end,
the leading end of the tube being adapted to engage means for
drilling a bore through the earth when a force is applied to the
trailing end of the tube; and
centralizer means on the tube to align the tube in the bore and to
prevent contact between the tube and sidewalls or the bore when the
tube is advanced therethrough, the centralizer means being a
buildup of non-metallic material around the periphery of the tube,
the buildup being surrounded by a metal sleeve.
2. The pipe of claim 1 in which the fiber reinforced synthetic tube
has a length in the range of about 20 feet to about 40 feet.
3. The pipe of claim 1 in which the fiber reinforced synthetic tube
has a density in the range of about 0.06 pounds per cubic inch to
about 0.08 pounds per cubic inch.
4. The pipe of claim 1 in which the buildup comprises glass
fibers.
5. The pipe of claim 4 in which a pin extends radially through the
metal sleeve and the buildup.
6. The pipe of claim 1 in which an adhesive bond is provided
between the metal sleeve and the buildup.
7. The pipe of claim 1 in which the centralizer means comprises a
series of radially extending buildups spaced axially along the tube
between the leading end and the trailing end.
8. The pipe of claim 1, including a liner which adhered to an inner
wall of the tube.
9. The pipe of claim 8 in which the liner is made of material
selected from the group consisting of plastic and elastomeric
material.
10. The pipe of claim 1, including a wear resistant outer coating
about the tube.
11. The pipe of claim 10 in which the coating comprises ceramic
beads in an epoxy compound.
12. The pipe of claim 1 in which the leading end of the tube has a
metal fitting and the trailing end of the tube has a metal fitting,
the metal fittings at the leading end and the trailing end being
complementary mating fittings whereby a plurality of tubes can be
serially connected to form a drilling string of desired length.
13. A drilling string for drilling a well bore, comprising:
a plurality of fiber reinforced synthetic tubes, each tube having a
leading end and a trailing end spaced axially from the leading
end,
the leading end of the first one of the tubes being engageable with
a bit for drilling a bore through the earth when a force is applied
to the trailing end of the last one of the tubes;
coupling means associated with the adjacent ends of each successive
pair of tubes for serially connecting the tubes and defining a
drilling string of desired length, the coupling means including a
pair of interchangeable fittings respectfully attached to the pair
of tubes, the end of one of the pair of tubes having an internal
taper and its respective fitting having an external taper; and
an adhesive bond between the internal taper of the tube and the
external taper of the fitting.
14. The drilling string of claim 13 in which one of the fittings
has an externally threaded portion and the other of the fitting has
an internally threaded portion for receiving the externally
threaded portion of the one fitting.
15. A drilling string for drilling a well bore, comprising:
a plurality of fiber reinforced synthetic tubes, each tube having a
leading end and a trailing end spaced axially from the leading
end,
the leading end of the first one of the tubes being engageable with
a bit for drilling a bore through the earth when a force is applied
to the trailing end of the last one of the tubes;
coupling means associated with the adjacent ends of each successive
pair of tubes for serially connecting the tubes and defining a
drilling string of desired length, the coupling means including a
pair of interchangeable fittings respectfully attached to the pair
of tubes, the end of one of the pair of tubes having an internal
taper and its respective fitting having an external taper; and
a metal sleeve extending around the internally tapered end of the
tube and the externally tapered end of the fitting when the fitting
is seated in the tube.
16. The drilling string of claim 15 in which an adhesive bond is
provided between the metal sleeve and the internally tapered end of
the tube.
17. The drilling string of claim 15 in which the metal sleeve is
welded to the fitting.
18. A drilling string for drilling a well bore, comprising:
a plurality of fiber reinforced synthetic tubes, each tube having a
leading end and a trailing end spaced axially from the leading
end,
the leading end of the first one of the tubes being engageable with
a bit for drilling a bore through the earth when a force is applied
to the trailing end of the last one of the tubes;
coupling means associated with the adjacent ends of each successive
pair of tubes for serially connecting the tubes and defining a
drilling string of desired length, the coupling means including a
pair of interchangeable fittings respectfully attached to the pair
of tubes, the end of one of the pair of tubes having an internal
taper and its respective fitting having an external taper; and
a pin extending radially through the internally tapered end of the
tube and the externally tapered end of the fitting.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally relates to drilling strings used to bore
wells in the earth and, more particularly, to a non-metallic pipe
for drilling a deviated well bore.
2. Background Art
As is generally known, underground petroleum reserves, water, and
soluble minerals often are accessed through vertical bores which
extend downwardly through the earth. To create a vertical bore, a
rotating metal tube having a leading bit or cutting element is
penetrated through the crust of the earth's surface and is advanced
downwardly until the tube reaches an oil bearing formation. The
drilling string then is withdrawn from the bore and oil or other
desired substances are pumped upwardly from the formation and
through the bore with known extraction techniques.
In an environment where a substance reserve cannot be accessed with
a conventional straight vertical well bore, directional drilling
techniques are used to create a deviated or extended-reach bore.
Generally, a flexible rotary drilling string is inserted through
the vertical portion of an existing straight well bore. When the
leading end of the drilling string reaches a predetermined depth,
the drill bit is deviated from the straight path and burrowed
through the sidewall of the existing well bore. The drilling string
continuously is advanced to create a relatively short-radius curved
bore having a substantially horizontal passage which can extend
hundreds of feet to reach an otherwise inaccessible oil bearing
formation, water supply, or mineral reserve.
It may be understood from the foregoing that in order to create a
suitable deviated well bore a drilling string must be sufficiently
flexible to permit continuous angular displacement of the string
while, at the same time, providing adequate structural integrity to
withstand the compression force and bending load which are induced
when the string is advanced through the earth. Moreover, while a
drilling string must be ductile enough to accommodate overall
angular deformation in excess of ninety degrees, the string must
also be capable of enduring the abuse inherent in the downhole
environment.
Attempts have been made at providing an acceptable drilling string
by connecting a number of short metal tubes, such as the
articulated drill pipe shown in U.S. Pat. No. 4,685,985 to Hatten,
issued Aug. 11, 1987 (see FIG. 1). The Hatten drill pipe, generally
designated 10, has a plurality of interlocked metal "jigsaw puzzle"
pipe sections 12 which are lowered through the straight portion of
a substantially vertical well bore 14. A cutting assembly 16 at the
leading end of the drill pipe then is deviated from the straight
path to create a curved bore 18. These types of drilling strings
have a number of problems.
Specifically, the articulated connection between successive pipes
is achieved with a dove-tail joint or a hinge Joint. Articulated
joints permit excessive and erratic movement of the articulated
pipe sections which, in turn, requires frequent directional
measurements and appropriate corrections to the orientation of the
bit to drill along a desired path. In addition, the joints
continuously open and close as the pipe rotates. Cuttings can enter
the openings and induce significant joint wear and degradation.
Metal drill pipes are very heavy and awkward to handle, making the
installation and operation of the drill pipe both cumbersome and
dangerous. The extreme weight of metal drill pipes produces large
friction forces when the pipe is rotated about an axis off
vertical, such as when the pipe is used to drill a horizontal bore.
The friction forces induce excessive wear of the articulated pipe
and thus limit the horizontal distance which can be drilled.
Moreover, the geometry of the "jigsaw puzzle" piece lobes in a
dove-tail joint may produce high stress concentrations which result
in fatigue failure after an unacceptably few number of cycles.
The present invention is directed toward overcoming one or more of
the problems set forth above.
SUMMARY OF THE INVENTION
An object of the invention, therefore, is to provide a composite
pipe assembly for drilling a deviated well bore in the earth.
In the exemplary embodiment of the invention, a plurality of
composite drill pipes or pipe sections are interconnected
end-to-end to form a flexible drilling string. An endmost composite
drill pipe has a fiber reinforced synthetic tube with a leading end
and a trailing end spaced axially from the leading end. The leading
end of the tube is engageable with a bit for drilling a bore
through the earth when a force is applied to the trailing end of
the tube. A centralizer is provided on the tube to align the tube
within the well bore and to prevent contact between the tube
exterior and the sidewalls of the bore when the tube is advanced
therethrough. The composite tube can have a length in the range of
about 20 feet to about 40 feet and can have a density in the range
of about 0.06 pounds per cubic inch to about 0.08 pounds per cubic
inch.
The centralizer consists of a buildup of glass fibers wrapped
around the periphery of the composite tube to create a radially
extending bulge. A steel sleeve encases the bulge and is attached
thereto by means of an adhesive bond between the sleeve and the
glass fibers and a series of circumferentially spaced pins which
extend radially through the sleeve and the buildup. A number of
centralizer buildups preferably are spaced axially along the length
of the tube between the leading end and the trailing end.
In operation of the drill pipe, fluid under pressure is forced into
the trailing end of the composite tube and is forced out through
the leading end of the tube to lubricate the bit and wash cuttings
outside the tube and toward the surface of the well through an
annulus between the outside of the drill pipe and the walls of the
oil well bore. A synthetic liner extends through the tube to
isolate the inner wall from fluid in the tube, and a wear resistant
outer coating shields the exterior of the tube from the cuttings
and other abrasive materials in the bore. The liner consists of an
elastomeric material, such as rubber, or, alternatively, can
consist of plastic. A suitable outer coating is formed of an epoxy
compound which contains ceramic beads.
In order to serially connect a number of drill pipes and form a
flexible drilling string of desired length, the leading end of each
composite tube has a metal fitting, such as a male fitting, and the
trailing end of each tube also has a metal fitting, such as a
female fitting. The male fittings and the female fittings are
complementary and interengageable, whereby the adjacent ends of a
plurality of successively arranged composite tubes are joined
together. More specifically, a male fitting has an externally
threaded portion which is received in an internally threaded
portion on an adjacent female fitting.
The fittings preferably are made of hardened steel and have an
external taper machined at an end opposite the threads. Each end of
the composite tube has an internal taper complementary to the
external taper on the fittings, and a metal fitting is seated in
each of the tapered tube ends and is adhesively bonded thereto.
Radial holes are drilled around the circumference of the tube ends
and into the steel fittings, and stainless steel dowel pins are
press fit into the holes to provide a mechanical lock between the
composite tube and the hardened steel fitting. A steel sleeve is
placed over the composite/steel interface and is welded to the
fitting and bonded to the outer surface of the tube.
Other objects, features and advantages of the invention will be
apparent from the following detailed description taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of this invention which are believed to be novel are
set forth with particularity in the appended claims. The invention,
together with its objects and advantages, may be best understood by
reference to the following description taken in conjunction with
the accompanying drawings, in which like reference numerals
identify like elements in the figures and in which:
FIG. 1 is a side elevational view of a prior art drilling
string;
FIG. 2 is a perspective view of a composite drill pipe according to
the invention used to create a drilling string;
FIG. 3 is a sectional view of the male metal end fitting on the
leading end of a composite drill pipe of the invention;
FIG. 4 is a sectional view of the female metal end fitting on the
trailing end of the composite drill pipe; and
FIG. 5 is a sectional view of one of the radial centralizers on the
composite drill pipe.
DETAILED DESCRIPTION OF THE INVENTION
As stated above with respect to FIG. 1, a prior art drill pipe,
generally designated 10, has a plurality of interlocked metal
"jigsaw puzzle" pipe sections 12 which are lowered through the
straight portion of a substantially vertical well bore 14. A
cutting assembly 16 at the leading end of the drill pipe then is
deviated from the straight path to create a curved bore 18.
Referring now to FIG. 2, an exemplary composite drill pipe is
generally designated 20 and has a fiber reinforced flexible
synthetic tube 22 which extends between a tube leading end 24 and a
tube trailing end 26. As noted above, a plurality of drill pipes 20
are interconnected end-to-end to form a flexible drilling
string.
To that end, the tube leading end has a pin connector 28 and the
tube trailing end has a complementary box connector 30 whereby a
plurality of drill pipes 20 may be serially connected to define a
drilling string of desired length. Moreover, tube leading end 24 is
engageable with a cutting tool or bit (not shown) for drilling a
bore through the earth when the tube is rotated and a downward
force is applied to tube trailing end 26. Generally, a single drill
pipe 20 has a length in the range of about twenty feet to about
forty feet, and a number of pipes are connected to define a
drilling string suitable for drilling a deviated well bore having a
radius of curvature in the range of twenty feet to forty feet.
Synthetic tube 22 has a density in the range of about 0.06 pounds
per cubic inch to about 0.08 pounds per cubic inch. A plurality of
radial centralizers 32 are spaced axially along the length of
synthetic tube 22 and serve to align the tube within a well bore to
prevent contact between the tube and the sidewalls of the bore when
the drill pipe is advanced therethrough.
In the exemplary embodiment of the invention, drill pipe 20 is
twenty-five feet long and weighs approximately ninety pounds. The
disclosed drill pipe has an inside diameter of approximately 1.5
inches, and the exterior diameter of the drill pipe is
approximately 2.6 inches. Radial centralizers 32 are equidistantly
spaced approximately 4.5 feet and have an outside diameter of
approximately 3.375 inches.
Synthetic tube 22 has a filament wound composite core 34 (see FIGS.
3-5) with a cylindrical internal passage 36 for supplying a cooling
and lubricating fluid to the drill bit at the bottommost end of a
drilling string. That is, as is generally known, "drilling mud" is
forced into the trailing end of a drill pipe and is forced out
through the leading end to lubricate the drill bit and wash
cuttings outside the tube. The drilling mud and cuttings are forced
upward toward the surface of the well through the annulus formed
between the outside of the drill pipe and the sidewalls of the well
bore.
A rubber liner 38 is bonded to the inside diameter of composite
core 34 and extends between tube leading end 24 and tube trailing
end 26 to protect the inside of the drill pipe from pressurized
drilling mud. While rubber offers sufficient flexibility and
impermeability, it should be understood that the invention also
envisions the use of a liner consisting of any elastomeric or
plastic material suitable for the stated purpose.
A wear resistant coating 40 may be applied over the exterior of
composite core 34 to protect the drill pipe from contact with the
washed cuttings. The drill cuttings that are circulated back up the
well bore are abrasive to the exterior of the composite core and
can cause significant damage to the structural fibers even if
exposed to the tube exterior for short lengths of time. A
preferable coating 40 consists of a high elongation epoxy compound
filled with wear resistant ceramic beads.
Pin connector 28 is shown in FIG. 3 and has a hardened steel end
fitting 42 bonded in leading end 24 of synthetic tube 22. The end
fitting has a threaded male nipple 44 and an opposite externally
tapered end 46 seated in a complementary taper 48 in the tube
leading end with an adhesive bond 50 formed therebetween. In
addition to the adhesive bond, the end fitting is mechanically
locked to the leading end of the tube by a plurality of
circumferentially spaced stainless steel dowel pins 52 (four shown
in FIG. 3). Radial holes are drilled around the circumference of
the tapered leading end of tube 22 and into end fitting 42. The
dowel pins then are press fit into the radial holes to interlock
the composite material and the steel end fitting. A steel sleeve 54
is drawn over the resulting joint between end fitting 42 and the
tube leading end and is abutted with an annular hub 56 on the end
fitting. The sleeve is welded to the steel end fitting, as at 58,
and is adhesively bonded to the tube end, as at 60.
Box connector 30 is shown in FIG. 4 and has a hardened steel end
fitting 62 bonded in trailing end 26 of synthetic tube 22. The end
fitting has an internally threaded female end 64 and an opposite
externally tapered end 66 seated in a complementary taper 68 in the
tube trailing end with an adhesive bond 70 formed therebetween. In
addition to the adhesive bond, the end fitting is mechanically
locked to the trailing end of the tube by a plurality of
circumferentially spaced stainless steel dowel pins 52 (four shown
in FIG. 4). As discussed above with respect to pin connector 28,
radial holes are drilled around the circumference of the tapered
trailing end of tube 22 and into end fitting 62. The dowel pins
then are press fit into the radial holes to interlock the composite
material and the steel end fitting. A steel sleeve 72 is drawn over
the resulting joint between end fitting 62 and tube end 26 and is
engaged in an annular recess 74 on the end fitting. The sleeve is
welded to the steel end fitting, as at 76, and is adhesively bonded
to the tube end, as at 78.
The exterior surface of a drill pipe is forced into the sidewalls
of an oil well bore when a drilling string is guided in a curved
path, thereby inducing unacceptable wear in the drill pipe leading
to eventual failure. The amount of contact wear is related directly
to the flexibility of the drill pipe. Thus, because unarticulated
steel is approximately ten times as stiff as composite material,
flexible drill pipe 20 experiences much less wear than would occur
in a metal pipe of the same geometry. Nevertheless, radial
centralizers 32 are provided to still further limit contact between
the drill pipe and the oil well bore.
Referring to FIG. 5, a centralizer 32 is shown in greater detail
and has a radial buildup or substructure 80 around the periphery of
composite core 34. Preferably, the radial buildup consists of
successively wound and bonded layers of glass fibers or other
filament which offers acceptable flexural characteristics. A sleeve
82 encases the filament substructure and is adhesively bonded
thereto, as at 84. In the exemplary embodiment shown, sleeve 82 is
made of stainless steel, however the invention fully comprehends
that the sleeve 82 comprise any non-magnetic metal whereby
electrical measuring equipment may be housed within the pipe during
drilling without subjecting electrical signals associated with the
equipment to magnetic characteristics of the drilling string.
Circumferentially spaced steel dowel pins 86 (two shown in FIG. 5)
extend radially through the steel sleeve and into the substructure.
The dowel pins preferably are welded to the sleeve to prevent the
pins from working loose during constant rotation and bending of the
drill pipe.
It will be understood that the invention may be embodied in other
specific forms without departing from the spirit or central
characteristics thereof. The present examples and embodiments,
therefore, are to be considered in all respects as illustrative and
not restrictive, and the invention is not to be limited to the
details given herein.
* * * * *